1. Field of the Invention
This invention relates in general to computer-implemented monitoring systems, and in particular, to a computer-implemented method and apparatus for graphically monitoring processes operating under statistical process control.
2. Description of Related Art
The technique of statistical process control (SPC) optimizes an industrial process by monitoring one or more characteristics of the process over time. SPC relies on a statistical analysis of process variables to ensure that the process is operating in a desired matter. SPC is based on the assumption that there is a random variation in the values of each variable that serves as a measure of the quality or efficiency of the process. To ensure that the process is in control, the values are measured at discrete intervals during the operation of the process. If the values consistently exhibit a normal distribution pattern within established limits, then the process is in statistical control. Variation from this normal distribution indicates that the process is not in statistical control. By plotting the values and comparing them with a desired target level, it is possible to detect undesirable shifts in the process. Once alerted, the operator can then take compensating steps to bring the process back under control.